{"cve":"CVE-2026-9803","nvd":{"published":"2026-05-28T06:16:29.750","modified":"2026-10-26T12:10:00.130","status":"Modified","description":"A flaw was found in Keycloak's ClientRegistrationAuth component. A remote unauthenticated attacker can exploit this vulnerability by sending a specially crafted POST request with a malformed 'Authorization: Bearer' header to any client registration endpoint. This can lead to an ArrayIndexOutOfBoundsException, causing the server to return an HTTP 500 error and resulting in a Denial of Service (DoS) for the affected service.","cvss_v4":null,"cvss_v3":{"version":"3.1","vector":"CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:L","score":5.3},"cwes":["CWE-125"],"references":["https://access.redhat.com/errata/RHSA-2026:25097","https://access.redhat.com/errata/RHSA-2026:25098","https://access.redhat.com/errata/RHSA-2026:30049","https://access.redhat.com/errata/RHSA-2026:30050","https://access.redhat.com/security/cve/CVE-2026-9803"],"products":["redhat:build_of_keycloak"],"source":"nvd","synced_at":"2026-10-26T12:35:18.182177120+00:00"},"epss":{"cve":"CVE-2026-9803","score":0.00417,"percentile":0.35765,"date":"2026-10-25"},"kev":null,"osv":[{"id":"GHSA-cpf7-j4cf-vqx4","url":"https://osv.dev/vulnerability/GHSA-cpf7-j4cf-vqx4","summary":"Keycloak has an Out-of-bounds Read","modified":"2026-07-01T21:56:29.587435Z","packages":[{"ecosystem":"Maven","name":"org.keycloak:keycloak-services","purl":"pkg:maven/org.keycloak/keycloak-services","ranges":["<=26.4.7"],"fixed":[]},{"ecosystem":"Maven","name":"org.keycloak:keycloak-services","purl":"pkg:maven/org.keycloak/keycloak-services","ranges":[">=26.5.0 <26.6.3"],"fixed":["26.6.3"]}]}],"attribution":["This product uses the NVD API but is not endorsed or certified by the NVD.","EPSS scores: FIRST Exploit Prediction Scoring System, https://www.first.org/epss","Known exploited vulnerabilities: CISA Known Exploited Vulnerabilities Catalog, https://www.cisa.gov/known-exploited-vulnerabilities-catalog","Package advisories: OSV (https://osv.dev), from the GitHub Advisory Database, PyPA, Go, RustSec and other ecosystem databases, under CC-BY 4.0 or CC0","CVE records: the CVE Program's CVE List (https://www.cve.org), under its terms of use (https://www.cve.org/Legal/TermsOfUse). CVE is a registered trademark of The MITRE Corporation; this product is not affiliated with the CVE Program."]}